Hair cutting appliances, particularly electric hair cutting appliances, are generally known and may include trimmers, clippers and shavers. Electric hair cutting appliances may also be referred to as electrically powered hair cutting appliances. Electric hair cutting appliances may be powered by electric supply mains and/or by energy storages, such as batteries, for instance. Electric hair cutting appliances are generally used to trim or cut (human) body hair, in particular facial hair and head hair to allow a person to have a well-groomed and well-styled appearance. Frequently, electric hair cutting appliances are also used for cutting animal hair.
U.S. Pat. No. 6,968,623 B2 discloses a hair trimmer comprising an adjustable comb, the hair trimmer further comprising a body, a cutting head including a blade set, wherein the comb is movable with respect to the blade set, an electric motor for driving the blade set to effect a cutting action, and an actuator assembly that is capable of moving the comb with respect to the blade set between a fully retracted position and a fully extended position, the actuator assembly comprising a comb carriage, a comb button connected to the comb carriage, wherein the comb button is actuable to adjust the position of the comb relative to the blade set, and a lock button that is movable with respect to the comb button, wherein the lock button selectively prevents and permits movement of the comb button relative to the body. Consequently, manual adjustment of the length of the comb is enabled.
U.S. Pat. No. 7,992,307 B2 discloses a hair clipper comprising a housing and a motor which is connected by a shaft to a motorized cutting guide, wherein the cutting guide is driven by the motor, wherein the cutting guide is movable to a plurality of guide positions. Consequently, motorized adjustment of the length of the cutting guide (or comb) is enabled.
A comb for a hair cutting appliance, particularly a spacing comb, may be generally arranged as an attachable comb or an integrally formed comb. A spacing comb generally spaces a blade set of the hair cutting appliance from the skin when the appliance is moved in a moving direction with respect to the skin during operation. Consequently, the spacing comb may enable to cut hair to a desired length, i.e. to a desired length of remaining hair at the skin.
Conventional hair cutting appliances may be fitted with a set of attachment combs, each of which is associated with a distinct hair length. Consequently, a user of the appliance basically needs to replace an attachment comb by another one to alter the hair length. Furthermore, manually adjustable comb attachments are known, as disclosed in U.S. Pat. No. 6,968,623 B2. Furthermore, also motorized or powered adjustment combs have been presented in recent years, as disclosed in U.S. Pat. No. 7,992,307 B2. Typically, powered adjustment combs comprise a movable comb portion that is movable with respect to the blade set of the hair cutting appliance, wherein the movable comb portion is coupled to an actuator, particularly to an electromotor and/or electric powertrain.
However, operating a motorized adjustment comb frequently has proven to be afflicted with several drawbacks. A motorized powertrain may, for instance, comprise a control unit that is capable of controlling the actuator (or motor). However, the control unit needs to be provided with respective input information, in particular with respect to an actual state or position of a movable comb portion with respect to the blade set. In other words, it may be desired to provide the control unit with absolute and/or relative (or incremental) positional information. The positional information may be indicative of an actual position of the movable comb portion. Based on the actual position, the control unit may operate the actuator for moving the movable comb portion to a desired destination position.
There are several approaches to the detection of the position or location of the movable comb portion of the adjustable spacing comb. Direct location detection may include sensors that are capable of directly detecting the (translatory) position of the movable comb portion. Consequently, these direct detection sensors basically need to be implemented in addition to and separate from a motorized powertrain for the spacing comb. Consequently, implementing a direct detection sensor that is capable of directly detecting a (translational) position of the spacing comb with respect to the blade set may be costly. An alternative approach may include the detection of rotations or revolutions of the actuator. With respect to the detection of the (true) position of the spacing comb with respect to the blade set, this approach may be referred to as indirect location detection, since a detected signal (e.g. number of rotations or amount of angular movement) needs to be converted into a desired (longitudinal) value. Consequently, the indirect detection approach may be afflicted with several drawbacks, for instance relatively large deviations between a derived (or calculated) positional value and a real positional value.
If the control unit is not aware of the actual position of the movable spacing comb, operating and adjusting the spacing comb may be further complicated. It would be therefore advantageous to present an adjustment drive for an adjustable spacing comb that comprises an improved location detection unit which may address at least some of the above-mentioned drawbacks. It would be further advantageous to provide an adjustable spacing comb and a hair cutting appliance fitted with such an adjustable spacing comb that may exhibit an improved location detection and comb adjustment performance. Preferably, the adjustment drive may be operated and controlled in a highly accurate and precise manner.
There is thus still room for improvement.